[LeetCode]151 Reverse Words in a String

public class Solution {

public String reverseWords(String s) {

// Solution A:
return reverseWords_Char(s);

// Solution B:
// return reverseWords_Split(s);
}

/////////////////////
// Solution A: Char
//
public String reverseWords_Char(String s) {

if (s == null)
return null;

char[] chars = s.toCharArray();
int len = chars.length;

StringBuilder sb = new StringBuilder();
StringBuilder subsb = new StringBuilder();

for (int i = 0 ; i < len ; i ++)
{
char c = chars[i];
if (c == ' ')
{
if (subsb.length() > 0)
{
if (sb.length() == 0)
sb.append(subsb.toString());
else
sb.insert(0, subsb.toString() + " ");
subsb = new StringBuilder();
}
}
else
subsb.append(c);
}
if (subsb.length() > 0)
{
if (sb.length() == 0)
sb.append(subsb.toString());
else
sb.insert(0, subsb.toString() + " ");
}

return sb.toString().trim();
}

/////////////////////
// Solution B: split
//
public String reverseWords_Split(String s)
{
if (s == null)
return null;
s = s.trim();
if (s.isEmpty())
return "";

String[] strs = s.split(" ");
StringBuilder sb = new StringBuilder();
for (int i = strs.length - 1 ; i >= 0 ; i --)
{
sb.append(strs[i]).append(" ");
}
return sb.toString().trim();
}
}